In rotary mechanisms, such as pumps, engines and compressors, having a rotor eccentrically supported for planetary movement in a housing cavity of multi-lobe, trochoidal configuration, bar seals are provided at the lobe junctures or at the apex portions of the rotor. These bar seals in conjunction with other seals elements isolate the working chambers formed between the rotor and housing from each other and surrounding areas. The bar seals may be employed in rotary piston mechanisms having a housing of epitrochoidal or hypotrochoidal configuration, as exemplified in the Japanese Pat. No. 50527 dated 1972 to Kogyo, British Pat. No. 583,035 dated Dec. 5, 1946 to Maillard, and U.S. Pat. No. 3,990,239 dated Nov. 9, 1976 to Pattas et al. Each of the bar seals is disposed for sliding movement in a slot or groove in the housing or rotor. A reciprocative movement is unavoidable because of necessary bearing clearances, timing gear back-lash, thermally caused distortions of the housing and rotor, and manufacturing tolerances. While composite bar seals were known prior to this invention, as exemplified in the U.S. Patents to Lamm, No. 3,685,922 dated Aug. 22, 1972; Schereberg, No. 3,672,798 dated Aug. 27, 1972; Lamm, No. 3,820,798 dated June 28, 1974; Antrim et al, No. 3,985,477 dated Oct. 12, 1976 and Rao, No. 3,873,249 dated Mar. 25, 1975, they suffer from one or more of the disadvantages of being heavy, rigid, weak and/or binding in their associated grooves.
It is, therefore, desirable to provide a bar seal which will slide within its associated groove with a minimum of friction to thereby insure that the bar seal will maintain continuous sealing contact pressure. Also, it would be desirable, particularly in compressors, for such bar seals to require no lubrication so that the problems of oil contamination of the gas being compressed is obviated. It has further been found advantageous for bar seals to be light in weight and conform to the possible irregularity of the surface with which it contacts to insure sealing integrity.
Accordingly, it is an object of this invention to provide a bar seal for a rotary piston mechanism which maintains continuous sealing contact pressure.
Another object of the present invention is to provide a bar seal for a rotary piston mechanism which requires no lubrication. A further object is to provide a bar seal which is relatively light in weight, providing a short time response to allow the pressure to cause the seal to conform to the sealing surface.
A still further object of this invention is to provide a bar seal for a rotary piston compressor which is flexible so as to insure continuous sealing contact along its length by conforming to minor irregularities in the sealing surface. At the same time sufficient strength is required to bridge over openings such as peripheral ports.
A feature of this invention is a body of material having self-lubricating characteristics, as for example, polytetrafluoroethylene (known by the trademark "Teflon") which may be mixed with bronze or other similar materials or compositions, secured to and at least covering portions of a base structure of high wear resistance characteristics, the base structure providing the sealing wear surface. The base structure may consist of cast iron or other well-known seal blade material.